Process for activating a web

ABSTRACT

A process for simultaneously activating two or more portions of a web in different directions. The process involves feeding a web into an apparatus that includes a pair of intermeshing activation rolls having three dimensional surface features configured to simultaneously activate different portions a web in different directions. The three dimensional surface features are arranged in discrete regions on the rolls such that at least two of the regions provide different directions of activation. The rolls include one or more buffer regions positioned between the discrete regions on the roll that provide different directions of activation.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No.61/003,620, filed Nov. 19, 2007.

FIELD OF THE INVENTION

The disclosure herein generally relates to a method for activating astretchable material. More specifically, the disclosure relates to amethod for simultaneously activating different areas of a stretchablematerial in different directions.

BACKGROUND OF THE INVENTION

Various articles, including disposable diapers, training pants, adultincontinence articles, feminine hygiene products, and the like utilizeelastic or elastic-like materials to improve the conformability and/orfit of the article. However, the relatively high costs typicallyassociated with some elastic materials may make their use in sucharticles undesirable. In addition, certain elastic materials may notprovide suitable softness, smoothness, strength, etc. when incorporatedinto a wearable article. As a result, nonwoven fabrics, especiallyinexpensive polymer-based nonwoven fabrics, have found increasingpopularity for use in disposable absorbent articles. Nonwoven fabricsare typically formed as webs, batts, mats, or sheets of fiber networks,and are sometimes referred to generally as “nonwoven webs.” An obstacleto the use of nonwoven webs in elastic textile articles has been therelatively inelastic nature of nonwoven webs formed from extensible butinelastic fibers. Therefore, laminates formed by joining a low-forcestretch elastic material to one or more layers of extensible nonwovenmaterial are typically used to reduce or even eliminate at least some ofthese undesirable features. In these constructions, the elastic layermay provide the elastic stretch needed for fit and comfort, while theouter nonwoven layers provide the aesthetics necessary to make thelaminate feel cloth-like. However, since the nonwoven is typically notelastic, it may still offer undesirable resistance to the extensibilityof the low-force stretch elastic material (i.e., “lock up” the stretchproperties of the elastic material).

One way to limit the amount of lock up caused by an inelastic materialsuch as an extensible nonwoven, when it is laminated to an elasticmaterial, is to activate the laminate. Activation, or incrementalstretching as it is sometimes referred to, involves permanentlystretching or elongating a web or portions of a web in one or moredirections. As the web is stretched, some of the fibers, inter-fiberbonds, and/or intra-fiber bonds are believed to be broken. The breakingof the fibers and/or bonds of the nonwoven web may result in increasedelasticity and/or softness in the web, at least to the degree ofelongation. Known processes for activating an extensible materialtypically involve passing the material through one or more pairs ofactivation rolls. The activation rolls generally have three-dimensionalsurface features (e.g., teeth and grooves, peaks and channels, orcorrugations), which are configured to operatively engage one another.The three-dimensional surface features on the rolls are typicallycomplementary (i.e., fit together in an intermeshing fashion) such thatthe rolls are sometimes referred to as being a “matched” or “mated”pair. As the web passes through the matched pair of activation rolls, itis subjected to relatively high localized mechanical stress from theintermeshing three-dimensional surface features. Most, if not all, ofthe fiber/bond breaking takes place in these areas of high localizedmechanical stress. Upon successful completion of the activation process,the activated web may exhibit an increase in length in one or moredimensions depending on the direction of activation.

In one known process for activating a material, a web is first fedthrough a pair of matched activation rolls that have raised portionsextending in the “axial direction” of the rolls (i.e., parallel to theaxis of rotation of the rolls) to activate the material in a firstdirection. The axially extending raised portions of the rolls intermeshin a manner similar to the way the teeth of two gears typicallyintermesh. The rolls may be positioned such that the intermeshing teethdo not substantially contact one another in order to avoid damaging theteeth and/or roll. As the web passes through the pair of rolls, it isactivated in the direction of travel of the material, sometimes referredto as the machine-direction (“MD”). In some instances, a matched pair ofrolls may include surface features that resemble a line of alternatingdiscs of larger and smaller diameters, sometimes referred to as aring-rolling configuration. Ring-rolling is typically used to activate aweb in the direction orthogonal to the machine direction, also referredto as the cross-direction (“CD”). In some instances, the nonactivatedweb may be bonded to an unstrained elastic material to form a laminatematerial. The laminate may subsequently be subjected to an activationprocess to form a “zero-strain” stretch laminate. Examples of methods ofactivating webs and/or methods of making elastic laminates that includeactivated materials may be found in U.S. Pat. No. 4,200,963 to Kamfe, etal.; U.S. Pat. No. 4,209,563 to Sisson; U.S. Pat. No. 4,525,407 to Ness;U.S. Pat. No. 4,834,741 to Sabee; U.S. Pat. No. 5,143,679 to Buell, etal.; U.S. Pat. No. 5,650,214 to Anderson et al., U.S. Pat. No. 5,156,793to Buell, et al.; U.S. Pat. No. 5,330,458 to Buell, et al.; U.S. Pat.No. 6,476,289 to Buell, et al.; U.S. Pat. No. 6,521,555 to Bodaghi, etal.; PCT Publication Nos. WO00/029199 to Jameson, et al.; WO03/072338 toMcAmish, et al.; WO05/110748 to McCormack et al.; and WO08/067463 toMiddlesworth, et al.; and U.S. Publication No. 20080224351 to Curro etal. While known processes may be suitable for activating a material inone direction, it may be desirable in certain applications to activate amaterial in more than one direction.

Another method for providing some elasticity to a substantiallyinelastic, extensible material is sometimes referred to as “SELFing,”which means Structural Elastic-Like Film. SELFing is similar toactivation in that the material is stretched between intermeshing teeth.However, in SELFing, the teeth do not run continuously along the lengthof the activation area and instead are discrete along the length,leaving narrow bands of nonactivated material. In the activated areas,the material deforms permanently, while in the unactivated areas, thereis substantially no permanent deformation. When a SELFed material isstretched, the material typically exhibits elastic properties.

One known method for activating a web in two directions is to pass theweb through a first pair of rolls that activate the web in a firstdirection, and then subsequently pass the web through a second (or more)pairs of rolls to activate the web in a second (or more) direction. Aproblem with adding additional pairs of rolls is that it may increasethe cost and complexity of a manufacturing operation. In addition,adding more pairs of rolls generally means more space is required on themanufacturing line to accommodate the additional rolls. Additionally, ifthe different areas of the web that are to have different directions ofactivation are relatively close to one another (e.g., less than 20 mmapart) it is possible that due to process tracking variability, a smallportion of the web may get activated twice, once in each of twodirections. This double activation may put excessive strain on the weblocally, resulting in pin holes, or in extreme cases, even tears in thelaminate. Thus, in at least some manufacturing processes, the additionalcost, complexity and/or space requirements may make the use ofadditional pairs of activation rolls undesirable.

Another known method for activating a web in two directions is to passthe web through a stamping operation that uses a pair of matched platesto activate portions of a web placed between the plates. The plates mayinclude three-dimensional surface features and are typically arranged asa complementary pair of plates with an upper plate and a lower plate.One of the plates, typically the upper plate, is moved by a piston orother means toward the other plate until the three-dimensional surfacefeatures of the plates intermesh to provide the desired depth ofengagement and corresponding level of activation. The three-dimensionalsurface features of the plates may be configured to provide activationin multiple directions and/or to different portions of a web. However,stamping operations tend to be slower than operations that employ a rolldue to the reciprocating nature of a press. In addition, the precisecontrol required for a proper depth of engagement and strain rate mayslow the process even further and/or require expensive equipment and/orcomplex processes. In at least some commercial industries, especiallythose industries where a high output of products may be required for theindustry to be commercially successful (e.g., the disposable diaperindustry), a stamping operation may not be a commercially desirable oreven commercially viable option for activating a web at high speeds.

Accordingly, it would be desirable to provide a method for activatingdifferent regions of a web in different directions with a single pair ofrolls without causing undesirable damage to the web.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a perspective view of a pair of activation rolls.

FIG. 2 is a side view of a pair of activation rolls.

FIG. 3 is a perspective view of a pair of activation rolls.

FIG. 4 is a side perspective view of an activation roll.

FIG. 5 is a front perspective view of an activation roll.

FIGS. 6A-6C are plan views of examples of activated webs.

FIGS. 7A-7C are plan views of examples of activated webs.

FIGS. 8A and 8B are plan views of an example of an activated web.

FIG. 9 is a plan view of an example of a disposable absorbent article.

DETAILED DESCRIPTION Definitions

“Absorbent article” means an article that is capable of absorbing andstoring liquid. A “wearable absorbent article” is a device that isplaced against or in proximity to the body of a wearer to absorb andcontain exudates that may be discharged from the body. Non-limitingexamples of wearable absorbent articles include diapers and trainingpants.

“Activation” is the mechanical deformation of an extensible materialthat results in permanent elongation of the extensible material in thedirection of activation in the X-Y plane of the material. For example,activation occurs when a web or portion of a web is subjected to astress that causes the material to strain beyond the onset ofplasticity, which may or may not include complete mechanical failure ofthe material or portion of the material. Activation of a laminate thatincludes an elastic material joined to an extensible material typicallyresults in the extensible material deforming plastically, while theelastic material returns substantially to its original dimension.“Activated” means a material that has been subjected to an activationprocess.

“Complementary” means the three-dimensional surface features of tworolls are configured to be relative opposites of one another when thesurface features overlap. For example, complementary surface featuresinclude a raised portion on a first roll that fits into the loweredportion of a second roll (and vice versa) when the surface features arebrought into close proximity of one another.

“Direction of activation,” means the direction, at any location on anactivation roll between two intermeshing surface features, that issubstantially perpendicular to the length direction of the intermeshingsurface features. For intermeshing surface features that are parallel toeach other, the direction of activation is perpendicular to the lengthdirection of both these surface features. For intermeshing surfacefeatures that are not parallel to each other, the direction ofactivation is the average of the two directions that are perpendicularto the length directions of each of the intermeshing surface features.For example, surface features in the form of teeth and grooves thatextend in the CD may provide activation in the MD, while surfacefeatures in the form of peaks and channels extending in a directionorthogonal to the axis of rotation of the roll may provide activation inthe CD. In other examples, the surface features on the activation rollmay be configured to activate the web in a continuous curvilineardirection (i.e., no gaps are present to separate the surface featuresinto discrete regions of activation) or a diagonal direction. Asdisclosed herein, activation in a continuous curvilinear direction isconsidered a single direction of activation. However, in certainembodiments, activation in an intermittent curvilinear direction (i.e.,breaks or gaps are present to separate the surface features intodiscrete regions of activation) may be considered different directionsof activation. A break or gap is a spatial separation between tworegions of activation where the shortest dimension in the break or gap,as measured between adjacent surface features, is greater than thesmallest pitch of the three-dimensional surface features in the discreteregions of activation separated by the break or gap. When the adjacentsurface features are the same height, then the gap size is thepeak-to-peak distance between the tips of the surface features. If theadjacent surface features are not the same height, then the gap size isthe shortest distance between the tip of the shortest surface featureand a point at the same relative height on the adjacent surface feature.

“Disposed” means the relative position of an element with regard toanother element. For example, a first element(s) that is formed (joinedand positioned) in a particular place or position as a unitary structurewith a second element or as a separate first structural element joinedto a second structural element, the first element may be said to bedisposed on the second element.

“Elastic” materials are materials that, upon application of a biasingforce, can stretch to an elongated length of at least about 150% or evento 200% of its relaxed, original length (i.e. can stretch to 50% or even100% more than its original length), without rupture or breakage.Further, upon release of the applied force, the material may recover atleast about 40%, at least about 60%, or even at least about 80% of itselongation. For example, a material that has an initial length of 100 mmcan extend at least to 150 mm, and upon removal of the force wouldretract to a length of 120 mm (i.e., exhibiting a 60% recovery).

“Extensible” materials are materials that upon application of a biasingforce, can stretch to an elongated length of at least about 150% or even200% of their relaxed, original length (i.e., can stretch to 50% or even100% more than its original length), without rupture or breakage.Further, upon release of the applied force, the materials show littlerecovery, for example less than about 40%, less than about 20%, or evenless than about 10% of their elongation. For example, a material thathas an initial length of 100 mm can extend at least to 150 mm, and uponremoval of the force would retract to a length of 140 mm (i.e.,exhibiting a 20% recovery).

“Intermesh” means complementary features that mesh together in anoverlapping fashion, but do not interlock or substantially constrain themotion of one another.

“Joined” means configurations whereby an element is directly secured toanother element by affixing the element directly to the other element,and configurations whereby an element is indirectly secured to anotherelement by affixing the element to an intermediate member(s) that inturn are affixed to the other element.

The “machine direction” or “MD” is the direction that is substantiallyparallel to the direction of travel of the web as it is activated.Directions within 45 degrees of the MD are considered to be machinedirectional. The “cross direction” or “CD” is the directionsubstantially perpendicular to the MD and in the plane generally definedby the web. Directions within 45 degrees of the cross direction areconsidered to be cross directional.

“Nonwoven” means a porous, fibrous material made from continuous (long)filaments (fibers) and/or discontinuous (short) filaments (fibers) byprocesses such as, for example, spunbonding, meltblowing, carding, andthe like. Nonwovens do not have a woven or knitted filament pattern.Nonwovens may be liquid permeable or impermeable.

“Outboard” and “inboard” mean, respectively, the location of an elementrelative to a second element with respect to the radial centerline of anactivation roll. For example, if element A is outboard of element B,then element A is further from the radial centerline than is element B.

“Stretchable” materials are materials that upon application of a biasingforce, can stretch to an elongated length of at least about 150% or even200%. Stretchable materials may be elastic or extensible depending onthe amount of recovery. An example of a stretchable material includes anextensible polypropylene nonwoven joined to an elastic polyethylenefilm.

“Three-dimensional surface feature” means an element of an activationroll that extends outwardly or inwardly from the roll, and is configuredto intermesh with a complementary three-dimensional surface feature ofanother activation roll to activate a web. Nonlimiting examples of threedimensional surface features include teeth, grooves, peaks, channels,and corrugations.

“Web” means a material capable of being wound into a roll. Webs may befilm webs, nonwoven webs, laminate webs, apertured laminate webs, etc.The face of a web refers to one of its two dimensional surfaces, asopposed to its edge. The term “composite web” refers to a web thatcomprises two or more separate webs that are bonded in a face to facerelationship. The bonding can be through the edges of the componentwebs, although the component webs lie in a face to face relationshipwith each other.

“X-Y plane” means the plane defined by the MD and CD of a moving web orthe length and width of a piece of material.

Apparatus

It is believed, without being limited by theory, that the amount oflocalized stress applied to a web in regions of the web where thedirection of activation changes abruptly (e.g., from CD activation to MDactivation in adjacent areas of the web) may be high enough toundesirably damage the web during the activation process. The damage tothe web may even be severe enough to render the web commerciallyunsuitable for its intended use (e.g., excessive pinholing, tearing,thinning, and/or weakening). In the areas of the web where the directionof activation changes abruptly, there may be insufficient space betweenthe three-dimensional surface features present on the activation rollsfor the web to occupy as it is being stretched and deformed by theactivation process. Spatially separating the areas of activation maysolve the problem of web damage, but then the material may lose some oreven all of its elastic properties in the areas bordering thenonactivated area because the nonactivated portions of the material mayundesirably constrain the stretch properties of the adjacent activatedportions. The loss of stretch in one or more portions of the web maydetract from the desired properties of the web, e.g., cloth-likeness,softness, stretchability. Surprisingly, it has been found that byplacing a suitable buffer region between regions on the roll thatprovide different directions of activation, the undesirable damage to aweb may be minimized or even eliminated during activation withoutcausing undesirable stretch “lock-up.”

The apparatus described herein includes a pair of intermeshingactivation rolls. The apparatus may be part of a larger manufacturingprocess, for example, a diaper manufacturing process, or the apparatusmay be a stand-alone device for activating a web. The rolls may vary insize, for example, from between 200 to 800 mm in diameter. The rolls maybe configured to have three-dimensional surface features such as, forexample, teeth, grooves, peaks, channels, corrugations, and the like.The rolls may each include a single surface feature, a plurality ofsurface features, a single region of surface features, or multipleregions of surface features. The rolls and their respective surfacefeatures may be formed from a unitary piece of material, or the surfacefeatures may be formed from discrete pieces of the same or differentmaterials and permanently or temporarily joined (e.g., removably and/orreattachably) to the roll before, during, and/or after formation of therolls. The rolls and the surface features may be made from the same ordifferent materials, and may include any suitable material known in theart. The three-dimensional surface features may be configured toactivate two or more portions of a web in different directionssimultaneously when the web is fed into a nip formed by the rotatingrolls. The term “simultaneously,” as used herein with regard toactivating a web in different directions, means that the activationprocess is accomplished using a single pair of rolls, as opposed to asequential operation which may use two or more pairs of rolls to providetwo or more different directions of activation. In contrast to knownmethods of stretching one or more portions of a web in multipledirections such as, for example, by biaxial activation and/or embossing,each discrete region of activation of the web, when activated by theprocess described herein, is activated in a single direction as opposedto the two or more directions of activation provided by other processes.It is believed, without being limited by theory, that limiting thedirection of activation in a particular region of a web to a singledirection may reduce the likelihood of damage to the web during theactivation process. Another difference between embossing, which istypically used to provide an image on a web as opposed to providingincreased extensibility, and activation is that during an embossingprocess the material that is embossed occupies substantially all of thespace between the male and female portions of the embossing pattern onthe two rolls. During activation, however, the material being activatedis stretched between two intermeshing three-dimensional surfacefeatures, one on each of the two rolls, but does not occupy all of thespace between these intermeshing surface features.

In certain embodiments, it may be desirable to activate one or moreportions of a web in the MD. MD activation may be accomplished byconfiguring one or more portions of each roll to include teeth thatextend parallel to the axis of rotation of the rolls. The roll willtypically include grooves disposed between adjacent teeth. The teeth andgrooves may be disposed on the activation roll such that they activateonly the portion of the web where MD activation is desired, for example,along one or more of the longitudinal sides of the web and less than,for example, 60 mm, 40 mm, 20 mm, 10 mm, or 5 mm inboard of thelongitudinal side edge. The dimensions of the portion of a roll thatincludes the teeth and grooves may be varied, as desired. In certainembodiments, it may be desirable to activate one or more portions of aweb in a direction other than the MD, e.g., the CD. Activating a web inthe CD may be accomplished by providing three-dimensional surfacefeatures that include peaks extending perpendicular to the axis ofrotation of the rolls. The surface features will typically includechannels disposed between adjacent peaks. The peaks and channels may bedisposed on the rolls so that they activate only the portion of the webwhere CD activation is desired, for example, inboard of the MD activatedportions. While this example discloses MD and CD activation, it is to beunderstood that the rolls may be configured to provide other directionsof activation including, without limitation, diagonal and/or curvilineardirections of activation.

The three-dimensional surface features may have a “pitch,” which is thedistance between the same relative points on the tips of two adjacentsurface features of the same type (e.g., the tip-to-tip distance betweentwo adjacent raised portions). The pitch may be varied as desired toprovide a suitable level of activation. Surface features having a lowerpitch typically provide more activation to a material, for the samedepth of engagement, than surface features having a higher pitch (i.e.,impart greater extensibility to the activated material). Suitable pitchvalues for the surface features disclosed herein include between 1 and10 mm, 2 and 8 mm, or 3 and 7 mm. In certain embodiments, the pitchbetween two surface features may vary depending on which points on thesurface features are chosen to determine the distance between the tips,e.g., nonparallel surface features configured to provide a curvilineardirection of activation. In such instances, the pitch is determined bymeasuring the distance between the midpoints of the tips of the surfacefeatures. The surface features may also have a height, which is thedistance from the surface of the roll to the tip of the surface feature,of between 2 and 20 mm. The tips of surface features may be flat orrounded. Rounded tips may place less stress on a web. The tips of thesurface features described herein may have a relatively high aspectratio, i.e., the length of the tip is substantially larger than thewidth. For example, the aspect ratio may be greater than 10, or evengreater than 100. The width of a particular surface feature may be,e.g., less than about 2 mm, less than 1 mm, or less than 0.5 mm.

In certain embodiments, particular portions of a web may be activated ina first direction (e.g., the MD, CD, or a curvilinear direction) by aparticular region of an activation roll. Other portions of the web,which are spatially separated by a buffer zone from the particularportion of the web activated in the first direction, may be activated ina second direction. Still other portions of the web, which are spatiallyseparated by a buffer zone from the particular portions of the webactivated in the first and second directions, may be activated in athird direction, and so on as desired. The intermeshing activation rollsmay include at least one buffer region on one or both of the rolls forseparating various regions of the rolls configured for activating a webin different directions, the buffer regions may correspond to bufferzones on the activated web. A buffer region may include nothree-dimensional surface features, relatively few three-dimensionalsurface features, or modified three-dimensional surface features (e.g.,teeth having a lower tooth height than other teeth on the same roll). Inembodiments where the buffer region includes three-dimensional surfacefeatures, the surface features provide little or even no activation. Forexample, the surface features may include teeth or peaks that do notprovide a sufficient depth of engagement or proper orientation toactivate a web passing between the rotating rolls. It is believed,without being limited by theory, that the portion of the web thatcorresponds to the buffer region on the roll may absorb at least some ofthe energy exerted by the activation rolls on the web during amulti-directional activation process and thereby reduce or even preventthe material failure that may be associated with simultaneousmulti-directional activation.

The buffer region may be any suitable size as long as the activated webis not substantially damaged as a result of activation and theextensibility of the activated portion of the web is not undesirablylocked up by a nonactivated buffer zone. The buffer region may becontiguous with the boundary of one or more “regions of activation” onan activation roll (i.e., discrete portions of the activation roll thatinclude three-dimensional surface features configured to activate aweb), and/or may partially or completely surround one or more regions ofactivation. The buffer region may extend in one or more of the CD, MD, acurvilinear direction or a diagonal direction. The width of the bufferregion is determined the same way as the gap size mentioned above,except that the adjacent surface features used in the measurement areconfigured to provide activation in different directions. Suitableexamples of buffer region widths include widths of between 2 and 30 mm,4 and 20 mm, or 6 and 10 mm. The width of a buffer region may or may notbe constant throughout the same buffer region. When an activation rollincludes more than one buffer region, the buffer regions may be the samewidth(s), but need not necessarily be so. It is to be understood that abuffer region spatially separates discrete portions of an activationroll configured to activate a web in different directions (e.g., CD andMD, CD and curvilinear, MD and curvilinear, MD and diagonal, and anycombination of these). Discrete portions of a roll which are configuredto activate a web in the same direction (e.g., MD and MD, CD and CD,curvilinear and curvilinear, diagonal and diagonal), but which arespatially separated from one another (e.g., to provide intermittentactivation in the same direction) are not separated by a buffer region,as contemplated herein. Discrete portions of an activation rollconfigured to activate a web typically have a surface area of >50 mm²,e.g., >5000 mm², or >50000 mm². The surface area of a region ofactivation is determined by measuring the surface area of thecorresponding activated area on a web activated by the roll. While thereis no absolute upper limit for the size of the particular area to beactivated, it is limited to less than 100%, e.g., <90%, <80%, <70, oreven <60%. For example, an activation roll used for activating an outercover for use in a disposable diaper or training pant may include two MDregions of activation that have a combined total surface area of 100 cm²for activating the leg band portions of the outer cover, and one CDregion of activation that has a total surface area of 900 cm² foractivating a body portion of the outer cover.

The three-dimensional surface features of the matched activation rollsdescribed herein are typically configured to intermesh. That is, thethree-dimensional surface features of one roll may be designed tooperatively engage the three-dimensional surface features of the otherroll such that the material to be activated, the rolls, and/or thethree-dimensional surface features are not undesirably damaged when therolls rotate and the material is passed between the rotating pair ofrolls. In certain embodiments, where the rolls include raised portions(e.g., teeth) separated by lowered portions (e.g., grooves), whichextend along the roll in a direction parallel to the axis of rotation ofthe roll, the raised portions of one roll may be configured to fit into(i.e., mesh) with the lowered portions of the other roll, and viceversa. In this way, the rolls, when rotated, may pass a web through atortuous, “zig-zag” path created by the intermeshing teeth and grooves,thereby activating the web in the MD. Activation in the CD may beaccomplished by configuring an intermeshing pair of rolls to have, e.g.,peaks and channels that extend perpendicular to the axis of rotation ofthe rolls. In certain embodiments, the intermeshing peaks and channelsmay be described as an alternating stack of two different diameterdisks. Disks with a larger diameter are alternated on the rolls withdisks that are smaller in diameter. The intermeshing pair of rolls isaligned so that the larger diameter disks of one roll are opposite thesmaller diameter disks of the other roller. In this way, the peaks andchannels that extend perpendicular to the axis of rotation of therollers intermesh.

A drive motor or other prime mover is typically utilized to drive atleast one of the rolls (“driven roll”). In embodiments where theactivation rolls include surface features in the form of intermeshingteeth and grooves that extend in a direction parallel to the axis ofrotation and where the intermeshing rolls remain in constant engagement(i.e., the intermeshing surface features are disposed around asubstantial portion of the circumference of the rolls), the second rolltypically need not be driven because torque will be transferred from thedriven roll through the web to the second roll. It may be desirable toconfigure the raised portions of the rolls so that they do not contactone another in a typical activation operation. It is to be understood,however, that one or more drive motors or other prime movers may be usedto drive one or both of the rolls. In addition, the rolls may each bemounted on a shaft that is positioned between two machine side plates.The first shaft may be located in fixed bearings while the other secondshaft is located in bearings in slidable members such that the positionof the slidable members is adjustable, e.g., by means of adjustingscrews or other devices known in the art. The adjusting device moves theslidable member, and thus the movable roll, respectively toward or awaythe stationary roll to further engage or disengage the gear-like teethof the pair of intermeshing rolls. The depth of engagement of the rollerteeth typically determines the degree of elongation to which the web issubjected. A balance is typically drawn between the depth of engagementof the roller teeth and the web composition, as these may affect thephysical properties of the activated web.

FIG. 1 shows an example of an apparatus 100 that includes a pair ofrotatable activation rolls 110 and 120. The rolls 110 and 120 mayinclude intermeshing teeth 111 and 121, opposing side edges 101 and 102,and a radial centerline 103 that extends through the radius of the roll110 or 120. The teeth 111 of the upper roll 110 are configured to fitinto (i.e., mesh) with the grooves 122 of the lower roll 120 when therolls rotate in opposite directions (i.e., clockwise andcounterclockwise, respectively, as indicated by the arrows). Likewise,the teeth 121 of the lower roll are configured to fit into with thegrooves 112 of the upper roll 110. A web 130 may be passed through therolls 110 and 120 in the MD to produce an activated web 135. In thisexample, the teeth 111 and 121 are shown as being coextensive with therolls 110 and 120 in the CD, however, it is to be understood that theteeth need not necessarily extend along the entire length of the roll,but may be configured to extend any distance on the roll 110 and/or 120,as desired.

FIG. 2 shows an example of an apparatus 200 that includes a pair ofrotatable rolls 210 and 220 having intermeshing teeth 211 and 221. Ascan be seen in FIG. 2, the teeth 211 of the upper roll 210 areconfigured to fit into the grooves 222 of the lower roll 220, and theteeth 221 of the lower roll 220 are configured to fit into the grooves212 of the upper roll 210 when the rolls 210 and 220 rotate. A web 230may be fed into the nip 240 formed between the rotating rolls 210 and220. As used herein, “nip” means the region where the surfaces of thetwo rolls 210 and 220 overlap or begin to overlap to receive and movethe web 230. After passing between the intermeshing three-dimensionalsurface features (211, 212, 221, and 222) of the rolls 210 and 220 inthe MD, the web 230 is activated and may have corrugations 235 or othervisible characteristics indicative of activation.

FIG. 3 shows an example of a pair of rotatable rolls 330 and 340 thatmay be suitable for activating a web in the CD. Each roll 310 and 320may include three-dimensional surface features 335 configured as analternating series of peaks 336, 346 and channels 337, 347 that form anoverall corrugated surface. The exact configuration, spacing and depthof the channels 337, 347 may vary, depending on, for example, the amountof elasticity desired in the activated portion of the fully processedweb. In certain embodiments, a pitch 350 of approximately 3.8 mm, anincluded angle of approximately 12° as measured at the peak, and apeak-to-groove valley depth of approximately 7.6 mm may be suitable.When the corrugated rolls are adjusted so that their opposing peaks 336,346 overlap one another to a depth of between, for example, 2 mm and 10mm, 5 mm and 7 mm, or 3.8 mm and 4.4 mm, good extensibilitycharacteristics may be produced in a web. The degree of overlap of theopposing peaks 336, 346 (i.e., the “depth of engagement”) on theaforementioned corrugated rolls 330, 340 may be adjusted, as desired, toproduce more or less extensibility in the activated portion of the web.For the aforementioned roll geometry and laminate web construction,peak-to-peak overlap depths ranging from as little as 1.27 mm to as muchas 5.71 mm may be achieved.

FIGS. 4-5 show perspective views of an example of a roll 400 thatincludes three-dimensional surface features for activating a web in twodifferent directions. The roll 400 may be configured to rotate in theclockwise direction, as indicated by arrows 470. The roll 400 mayinclude three-dimensional surface features in the form of teeth 446separated by grooves 447 between the teeth 446. While not shown, it isto be understood that the roll 400 is one roll of a pair of intermeshingmatched rolls, and that the second roll in the pair will have surfacefeatures which complement the surface features of the roll 400 shown inFIGS. 4-5. The pitch of the teeth 446 may be the same for all teeth 446on the roll 400 or different, depending on the location, amount, rate,and direction of activation desired. The teeth 446 and the grooves 447between the teeth 446 may be configured to extend across the roll 400 ina direction parallel to the axis of rotation so as to provide MDactivation to a portion or portions of a web. A single region 440 ofteeth 446 and grooves 447 may be configured to activate a particularportion or portions of a web in the MD only one time for each completerevolution of the roll 400 (i.e., 360° of rotation). An opposing region441 of teeth 446 and grooves 447 may be included on the opposite side,axially, of the roll 400 to provide, e.g., a web having MD activatedportions that are symmetrical in the CD. A region 440, 441 may includeany number of the same or different sized teeth 446 and grooves 447suitable for providing the desired activation. A region 440, 441 isdistinguished from another region 440, 441 by a discernible spatialseparation between the two regions 440 and 441, such as space 405. Incertain embodiments, the roll 400 may include one or more regions 440,441 of teeth 446 and grooves 447 positioned continuously around theentire circumference of the roll 400 so as to provide continuousactivation of a moving web in the MD. In certain embodiments, regions440, 441 of teeth 446 and grooves 447 may be intermittently positioned(i.e., spatially separated) around the circumference of the roll 400 toprovide areas of MD activation on a web that are intermittent in the MD.For example, two or more regions 440, 441 of teeth 446 and grooves 447equally spaced around the circumference of the roll 400, but separatedby a break(s) or gap(s), may provide areas of MD activation on a movingweb that are equidistantly separated in the MD. FIG. 6A shows an exampleof a web 600 having MD activated areas 610 that are continuous in the CDand intermittent in the MD. In certain embodiments, regions 440, 441 ofteeth 446 and grooves 447 may be spaced apart in the axial direction toprovide areas of MD activation on a web that are intermittent in the CD.FIG. 6B shows an example of a web 620 having MD activated regions 630that are continuous in the MD and intermittent in the CD. In certainembodiments, regions 440, 441 of teeth 446 and grooves 447 may beconfigured to activate one or more portions of a web intermittently inthe MD and CD. FIG. 6C shows an example of a web 640 having MD activatedareas 650 that are intermittent in the CD and MD. In addition,particular portions of the web 640 may be activated at higher levels(i.e., have greater extensibility) than other areas that are activatedin the same direction. The higher activated areas 651 and loweractivated areas 652 may be positioned in any desirable configuration onthe web.

The roll 400 may include three-dimensional surface features in the formof peaks 436 separated by channels 437 between the peaks 436. The pitchof the peaks 436 may be the same for all peaks 436 on the roll 400 ordifferent, depending the location, amount, rate, and direction ofactivation desired. The peaks 436 and channels 437 may be disposed in acontinuous configuration around substantially the entire circumferenceof the roll 400 in order to continuously activate a particular portionor portions of a moving web in the CD. In certain embodiments, the peaks436 and channels 437 may be disposed such that they extend onlypartially around the circumference of the roll 400 in order to provideCD activation once for each complete revolution of the roll 400. Incertain embodiments, regions 470 of peaks 436 and channels 437 may beintermittently positioned around the circumference of the roll 400 toprovide one or more areas of CD activation on a web that areintermittent in the MD. For example, two or more regions 470 of peaks436 and channels 437 spaced around the circumference of the roll 400,but separated by a break(s) or gap(s), may provide areas of CDactivation on a web that are intermittent in the MD. FIG. 7A shows anexample of a web 700 having CD activated areas 710 that are continuousin the CD and intermittent in the MD. In certain embodiments, regions ofpeaks 436 and channels 437 may be spaced apart in the axial direction toprovide areas of CD activation on a web that are intermittent in the CD.FIG. 7B shows an example of a web 720 having CD activated areas 730 thatare continuous in the MD and intermittent in the CD. In certainembodiments, regions of peaks 437 and channels 437 may be configured toprovide areas of CD activation 750 on a web 740 that are intermittent inthe MD and CD, for example, as shown in FIG. 7C.

The roll 400 may include a circumferential buffer region 450 and anaxial buffer region 460. The circumferential buffer region 450 may beconfigured to separate regions of directionally different activation inthe axial direction. The circumferential buffer region 450 has a width(W_(cd)), which may be, e.g., any value that falls within the range ofbetween 2 and 30 mm. The axial buffer region 460 may be configured toseparate regions of directionally different activation extend in thecircumferential direction (i.e., around the circumference of the roll400). The axial buffer region 460 has a width (W_(md)), which may be,e.g., any value that falls within the range of between 2 and 30 mm. Theaxial and circumferential buffer regions 460 and 450 may extend in anydirection within 45° of the axial direction or the circumferentialdirection (as measured in the plane defined by the surface of the roll).The roll 400 may include one or more buffer regions positioned toseparate any number of surface features and/or regions of surfacefeatures, which are configured to activate a web in differentdirections.

The three-dimensional surface features and the buffer region(s) 450, 460of the roll 400 may be arranged to provide any suitable configuration ofintermittent and/or continuous activation pattern, as desired. FIG. 8Ashows an example of a web 800 having MD activated portions 810 that arecontinuous in the MD and intermittent in the CD, and CD activatedportions 820 that are continuous in the CD and intermittent in the MD.FIG. 8A shows the web 800 as including a buffer zone 830 between the CDactivated portion 820 and the MD activated portions 810. In certainembodiments, the web 800 may include continuous curvilinear directionactivated portions 840, and CD activated portions 850, as shown in FIG.8B. The curvilinear direction activated portions 840 and the CDactivated portions 850 may be separated by a buffer zone 860.

In certain embodiments, an apparatus that includes a pair ofintermeshing activation rolls may be configured to activate a particularnumber of articles and/or a particular number of portions of a singlearticle for each revolution of the activation rolls. Thethree-dimensional surface features of the rolls may be circumferentiallyspaced around the roll to activate any number of articles per revolution(e.g., 2, 3, 4, 5, 6, 7, 8, 9, or even 10 or more) and/or any number ofportions of a single article (e.g., 2, 3, 4, 5, 6, 7, 8, 9, or even 10or more). For example, the rolls may be configured as 5-up rolls. In a5-up configuration, the rolls may include five regions of complementarythree-dimensional surface features circumferentially spaced 72° apartaround each roll. In such a configuration, the rolls may be capable ofactivating a continuous moving web up to 5 times in the MD and/or CD foreach revolution of the rolls, which may correspond to activating fivedifferent articles, five portions of a single article, or anycombination thereof. It is to be understood that the number of articlesor portions of a single article activated in a single revolution neednot necessarily be the same for each revolution. For example, the rollsmay be configured to activate four articles or portions of an article inone revolution and five articles or portions of an article in asubsequent revolution. It is to be further understood that thethree-dimensional surface features (or regions thereof) may bepositioned on the rolls in any suitable configuration to provide thedesired number of activations per revolution, and that in embodimentswhere the rolls are configured to activate a web multiple times in asingle revolution, the surface features need not be configured toactivate the web at the same rate or the same amount.

Disposable Absorbent Article

FIG. 9 shows an example of a disposable absorbent article 20 in a flat,uncontracted state. The disposable absorbent article 20 of FIG. 9 may bea wearable article such as a disposable diaper or training pant. Thedisposable absorbent article 20 may be arranged in a fastenedconfiguration (i.e., the article 20 may be fastenable, refastenable, orprefastened) to form a waist opening and at least one leg opening. Thedisposable absorbent article 20 may include a longitudinal centerline 10that extends in the longitudinal direction (Y) and a lateral centerline86 that extends in the lateral direction (X). The longitudinal andlateral directions may be parallel to the MD and CD, respectively. Thedisposable absorbent article 20 may include a liquid permeable topsheet24, an outer cover 22, and an absorbent core 26 disposed between thetopsheet 24 and the outer cover 22. The outer cover 22 may include a legband portion 33. The leg band portion 33 of the outer cover 22 mayencircle the entire circumference of the leg opening when the article 20is in a fastened configuration. The disposable absorbent article 20 mayinclude one or more elastic strands or elastic leg bands 32 joined tothe leg band portion 33. The leg band 32 may be coextensive with the legband portion 33, but need not necessarily be so. The leg band 32 mayinclude an elastic material layer (e.g., strands, film, or nonwoven)laminated with one or more layers of extensible nonwoven and/or films.The leg band 32 may be a live stretch or zero-strain stretch laminates.In a live stretch laminate, the elastic material is typically stretchedto some extent prior to lamination to an extensible nonwoven. Oneadvantage of live stretch localized stress to the laminate may bereduced during activation. However, live-stretch laminates may requiremore nonwoven material than zero-strain laminates, and thus be moreexpensive. The leg band may be attached flush with, laterally inboard,or laterally outboard of the side edge of the outer cover in the crotchregion. The leg band 32 and/or leg band portion 33 of the outer cover 22may be activated continuously or intermittently to provide a stretchableleg opening when the disposable absorbent article is in a fastenedconfiguration.

The disposable absorbent article 20 may include a front waist region 36,a rear waist region 38 opposed to the front waist region 36, and acrotch region 37 located between the front waist region 36 and the rearwaist region 38. The waist regions 36 and 38 generally comprise thoseportions of the disposable absorbent article 20 which, when worn,encircle the waist of the wearer. The crotch region 37 is that portionof the disposable absorbent article 20 which, when the disposableabsorbent article 20 is worn, is generally positioned between the legsof the wearer. The waist regions 36 and 38 and the crotch region 37,except for those portions of the article 20 or outer cover 22 thatinclude the leg band portion(s) 33, may collectively be referred to asthe body 30 of the article 20 or outer cover 22. As shown in FIG. 9, theouter periphery of the disposable absorbent article 20 is defined bylongitudinal side edges 54 and end edges 56. The disposable absorbentarticle 20 may include longitudinal side edges 54 that are orientedgenerally parallel to the longitudinal centerline 10. The outer cover 22may include edges that are coterminous with the longitudinal side edges54 and/or end edges 56 of the disposable absorbent article 20.Alternatively, the outer cover 22 may have one or more edges that arepositioned inboard of the respective edges 54, 56 of the disposableabsorbent article 20, but which are oriented in generally the samedirection (i.e., parallel to the longitudinal and lateral centerlines 10and 86).

Disposable absorbent articles such as disposable diapers are generallydesigned to provide a suitable fit around the waist and legs of awearer. Due to a variety of physical differences in wearers, thecircumferences, shapes, and other physical characteristics of a wearer'swaist or legs may vary widely between wearers, and thus require a rangeof sizes of absorbent articles. Therefore, it may desirable to provide adisposable absorbent article that is able to adjust to a variety ofwearer sizes, for example, by providing an outer cover that hasmultidirectional elasticity. Such an outer cover may include an outerextensible nonwoven layer that has a cloth-like appearance and feel andan inner elastic layer. The outer and inner layers may be joined totogether to form a laminate. In order to provide a disposable diaper orpant with underwear-like properties, it may be desirable to activate allor a portion of the outer cover of such articles in the CD so that whenthe outer cover is incorporated into the article (e.g., a disposablediaper or training pant), the article will provide a desirable fit byelastically conforming to a wearers body in the waist regions (e.g.,across the upper portion of the buttocks). It may also be desirable toactivate the leg band portion of the outer cover in the MD to provide360 degree stretch around the leg opening when the diaper or pant isworn by an intended wearer. In certain embodiments, the leg band portionmay be activated in a curvilinear direction to follow the contour of thelongitudinal side edge of the outer cover. The different directions ofactivation (e.g., the CD activated body portion of the outer cover andthe MD activated leg band portion of the outer cover) may be spatiallyseparated on the outer cover by one or more buffer zones. The bufferzone may be partially or entirely bounded by and/or contiguous with twoor more regions of the disposable absorbent article having differentdirections of activation. The buffer zone may be between 2 and 30 mmwide. The apparatus and process described herein may be suitable forsimultaneously activating such an outer cover without causingundesirable damage to the outer cover web or undesirable stretchlock-up. All documents cited in the Detailed Description of theInvention are, in relevant part, incorporated herein by reference; thecitation of any document is not to be construed as an admission that itis prior art with respect to the present invention. To the extent thatany meaning or definition of a term in this written document conflictswith any meaning or definition of the term in a document incorporated byreference, the meaning or definition assigned to the term in thiswritten document shall govern.

The dimensions and values disclosed herein are not to be understood asbeing strictly limited to the exact numerical values recited. Instead,unless otherwise specified, each such dimension is intended to mean boththe recited value and a functionally equivalent range surrounding thatvalue. For example, a dimension disclosed as “40 mm” is intended to mean“about 40 mm.”

Every document cited herein, including any cross referenced or relatedpatent or application, is hereby incorporated herein by reference in itsentirety unless expressly excluded or otherwise limited. The citation ofany document is not an admission that it is prior art with respect toany invention disclosed or claimed herein or that it alone, or in anycombination with any other reference or references, teaches, suggests ordiscloses any such invention. Further, to the extent that any meaning ordefinition of a term in this document conflicts with any meaning ordefinition of the same term in a document incorporated by reference, themeaning or definition assigned to that term in this document shallgovern.

While particular embodiments of the present invention have beenillustrated and described, it would be obvious to those skilled in theart that various other changes and modifications can be made withoutdeparting from the spirit and scope of the invention. It is thereforeintended to cover in the appended claims all such changes andmodifications that are within the scope of this invention.

1. A method for simultaneously activating a stretchable material inmultiple directions, the method comprising: feeding the stretchablematerial into a nip formed between a first rotatable roll and a secondrotatable roll, wherein the first and second rolls comprise a firstregion comprising a least one three-dimensional surface feature, thethree-dimensional surface feature(s) of the first region of the firstroll and the three-dimensional surface feature(s) of the first region ofthe second roll being complementary to one another and positionedrelative to one another such that when the first roll and the secondroll are rotated the three-dimensional surface features of the firstregions of the first and second rolls intermesh, the intermeshingsurface features being operatively configured to activate thestretchable material in a first direction; a second region comprising atleast one three-dimensional surface feature, the three-dimensionalsurface feature(s) of the second region of the first roll and thethree-dimensional surface feature(s) of the second region of the secondroll being complementary to one another and positioned relative to oneanother such that when the first roll and the second roll are rotatedthe three-dimensional surface features of the second regions of thefirst and second rolls intermesh, the intermeshing surface features ofthe second regions of the first and second rolls being operativelyconfigured to activate the stretchable material in a second directionwhich is different from the first direction; and a circumferentialbuffer region disposed between the portions of the first and secondregions that include three-dimensional surface features.
 2. The methodof claim 1, wherein the buffer region has a width of between about 2 and30 mm.
 3. The method of claim 1, wherein the buffer region has a widthof between about 5 and 20 mm.
 4. The method of claim 1, wherein thethree-dimensional features of at least one of the first and secondregions comprise raised portions having a pitch of at least 1 mm.
 5. Themethod of claim 1, wherein the first and second rolls are configured torotate 360 degrees, and the first and second rolls are configured toactivate the stretchable material two or more times for each 360 degreesof rotation.
 6. The method of claim 1, wherein the first and secondrolls are configured to rotate 360 degrees and the stretchable materialcomprises discrete articles, and wherein the first and second rolls areconfigured to activate two or more articles for each 360 degrees ofrotation.
 7. The method of claim 1, wherein the rolls are configured toactivate the stretchable material intermittently in at least one of themachine direction and the cross direction.
 8. The method of claim 1,wherein the first direction is the machine direction and the rolls areconfigured to continuously activate the stretchable material in thecross direction.
 9. The method of claim 1, wherein the first and seconddirections of activation are selected from the group consisting of amachine direction, a cross direction, a diagonal direction, and acurvilinear direction.
 10. The method of claim 1, wherein thestretchable material comprises an extensible material joined to anelastic material, the stretchable material being suitable for use as anouter cover for a disposable absorbent article.
 11. The method of claim10, wherein the stretchable material comprises a body portion and a legband portion and the first regions are configured to activate the bodyportion and the second regions are configured to activate the leg bandportion.
 12. The method of claim 10, wherein the body portion isactivated in the cross direction and the leg band portion is activatedin the machine direction.
 13. The method of claim 12, wherein the legband portion includes a leg band attached thereto.
 14. The method ofclaim 1, wherein at least one of the first and second rolls comprise anaxial buffer region and a circumferential buffer region.
 15. The methodof claim 1, further comprising a single step of a multi-step diapermanufacturing process.
 16. The method of claim 15, wherein thestretchable material is suitable for use as an outer cover in adisposable diaper and the single step comprises activating the outercover.
 17. The method of claim 1, wherein the first and second rollsinclude a third region configured to provide a third direction ofactivation that it is different than the first and second directions ofactivation and wherein a second buffer region is disposed between thethird region and at least one of the first and second regions.
 18. Themethod of claim 1, wherein first and second rolls include a third regionconfigured to activate the stretchable material in the second direction,the second and third regions configured to activate different portionsof the stretchable material.
 19. The method of claim 18, wherein atleast a portion of the first and second regions and at least a portionof the first and third regions are separated by a buffer region.
 20. Themethod of claim 18, wherein the second and third regions arerespectively disposed on first and second axially opposed ends of thefirst and second rolls, the second and third regions extending axiallyinward from their respective ends no more than 60 mm.